Electronic Devices with High Frequency Polarization Optimization

ABSTRACT

A first device may generate optical signals of different polarizations. Photodiodes may use the optical signals to transmit wireless signals at different polarizations and at a frequency greater than 100 GHz using the optical signals. A second device may receive the wireless signals and may convert the wireless signals into optical signals. A Stokes vector receiver on the second device may generate Stokes vectors based on the optical signals. Control circuitry on the second device may use the Stokes vectors generated for a series of training data in the wireless signals to generate a rotation matrix that characterizes polarization rotation between the first and second devices. The control circuitry may multiply wireless data in subsequently received wireless signals by the rotation matrix to mitigate the polarization rotation and other transmission impairments while using minimal resources.

This application claims the benefit of U.S. Provisional PatentApplication No. 63/247,176, filed Sep. 22, 2021, which is herebyincorporated by reference herein in its entirety.

FIELD

This disclosure relates generally to electronic devices and, moreparticularly, to electronic devices with wireless circuitry.

BACKGROUND

Electronic devices are often provided with wireless capabilities. Anelectronic device with wireless capabilities has wireless circuitry thatincludes one or more antennas. The wireless circuitry is used to performcommunications using radio-frequency signals conveyed by the antennas.

As software applications on electronic devices become moredata-intensive over time, demand has grown for electronic devices thatsupport wireless communications at higher data rates. However, themaximum data rate supported by electronic devices is limited by thefrequency of the radio-frequency signals. In addition, if care is nottaken, impairments such as misalignment between an electronic device andexternal equipment can limit communication efficiency in scenarios wheresignals are conveyed between the electronic device and the externalequipment using multiple electromagnetic polarizations.

SUMMARY

A wireless communication system may include a central optical processorand an access point. The central optical processor may generate firstoptical signals at a first frequency and having a first polarization,second optical signals at the first frequency and having a secondpolarization, and third optical signals at a second frequency that isdifferent from the first frequency. An optical combiner may combine thefirst, second, and third optical signals onto an optical fiber. Theoptical fiber may illuminate a first photodiode in the access pointusing the first optical signal and the third optical signal. The opticalfiber may illuminate a second photodiode in the access point using thesecond optical signal and the third optical signal.

The first photodiode may transmit first wireless signals having thefirst polarization over a first antenna radiating element based on thefirst and third optical signals. The second photodiode may transmitsecond wireless signals having the second polarization over a secondantenna radiating element based on the second and third optical signals.The first and second wireless signals may be transmitted at a frequencygreater than or equal to 100 GHz. An electronic device may receive thefirst and second wireless signals. The first optical signal may bemodulated to include a series of training data. The training data may beused by the electronic device to mitigate polarization rotations andother transmission impairments.

The electronic device may include a first antenna radiating element thatreceives the first wireless signals and a second antenna radiatingelement that receives the second wireless signals. The electronic devicemay include a first photodiode that converts the first wireless signalsto fourth optical signals using an optical local oscillator and a secondphotodiode that converts the second wireless signals to fifth opticalsignals using the optical local oscillator. The electronic device mayinclude a Stokes vector receiver that generates Stokes vectors based onthe fourth and fifth optical signals. One or more processors on theelectronic device may use the Stokes vectors generated for the series oftraining data to generate a rotation matrix that characterizes thepolarization rotation between the electronic device and the wirelesscommunications system. The one or more processors may multiply thewireless data in subsequently received wireless signals by the rotationmatrix to mitigate the polarization rotation and other transmissionimpairments while using minimal resources.

An aspect of the disclosure provides an electronic device. Theelectronic device can include a first antenna radiating elementconfigured to receive a first wireless signal of a first polarization ata frequency greater than or equal to 100 GHz. The electronic device caninclude a second antenna radiating element configured to receive asecond wireless signal of a second polarization that is different fromthe first polarization. The electronic device can include a firstphotodiode coupled to the first antenna radiating element and configuredto convert the first wireless signal into a first optical signal. Theelectronic device can include a second photodiode coupled to the secondantenna radiating element and configured to convert the second wirelesssignal into a second optical signal. The electronic device can include aStokes vector receiver coupled to the first photodiode over a firstoptical path and coupled to the second photodiode over a second opticalpath.

An aspect of the disclosure provides a method of performing wirelesscommunications using an electronic device. The method can include withone or more antennas, receiving first wireless signals of a firstpolarization and second wireless signals of a second polarization thatis different from the first polarization. The method can include with afirst photodiode, converting the first wireless signals into firstoptical signals. The method can include with a second photodiode,converting the second wireless signals into second optical signals. Themethod can include with a receiver, generating Stokes vectors based onthe first optical signals and the second optical signals. The method caninclude with one or more processors, generating a rotation matrix basedon the Stokes vectors. The method can include with the one or moreprocessors, applying the rotation matrix to wireless data in subsequentwireless signals received using the one or more antennas.

An aspect of the disclosure provides a wireless communication system.The wireless communication system can include a first photodiode. Thewireless communication system can include a first antenna coupled to thefirst photodiode. The wireless communication system can include a secondphotodiode. The wireless communication system can include a secondantenna coupled to the second photodiode. The wireless communicationsystem can include a first light source configured to generate a firstoptical signal at a first frequency and having a first polarization andconfigured to generate a second optical signal at the first frequencyand having a second polarization orthogonal to the first polarization.The wireless communication system can include a second light sourceconfigured to generate a third optical signal at a second frequency thatis different from the first frequency. The wireless communication systemcan include an optical combiner configured to combine the first opticalsignal, the second optical signal, and the third optical signal onto anoptical path, the optical path being configured to illuminate the firstphotodiode using the first optical signal and the third optical signaland being configured to illuminate the second photodiode using thesecond optical signal and the third optical signal, the first photodiodebeing configured to transmit first wireless signals having the firstpolarization over the first antenna based on the first optical signaland the third optical signal, and the second photodiode being configuredto transmit second wireless signals having the second polarization overthe second antenna based on the second optical signal and the thirdoptical signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an illustrative electronic device havingwireless circuitry with at least one antenna that conveys wirelesssignals at frequencies greater than about 100 GHz in accordance withsome embodiments.

FIG. 2 is a top view of an illustrative antenna that transmits wirelesssignals at frequencies greater than about 100 GHz based on optical localoscillator (LO) signals in accordance with some embodiments.

FIG. 3 is a top view showing how an illustrative antenna of the typeshown in FIG. 2 may convert received wireless signals at frequenciesgreater than about 100 GHz into intermediate frequency signals based onoptical LO signals in accordance with some embodiments.

FIG. 4 is a top view showing how multiple antennas of the type shown inFIGS. 2 and 3 may be stacked to cover multiple polarizations inaccordance with some embodiments.

FIG. 5 is a top view showing how stacked antennas of the type shown inFIG. 4 may be integrated into a phased antenna array for conveyingwireless signals at frequencies greater than about 100 GHz within acorresponding signal beam.

FIG. 6 is a circuit diagram of illustrative wireless circuitry having anantenna that transmits wireless signals at frequencies greater thanabout 100 GHz and that receives wireless signals at frequencies greaterthan about 100 GHz for conversion to intermediate frequencies and thento the optical domain in accordance with some embodiments.

FIG. 7 is a circuit diagram of an illustrative phased antenna array thatconveys wireless signals at frequencies greater than about 100 GHzwithin a corresponding signal beam in accordance with some embodiments.

FIG. 8 is a diagram showing how an illustrative central opticalcontroller may provide optical signals to an access point for conveyingmultiple polarizations of wireless signals at frequencies greater thanabout 100 GHz based on the optical signals in accordance with someembodiments.

FIG. 9 is a circuit diagram showing how an illustrative central opticalcontroller may generate optical signals that are provided to an accesspoint for conveying multiple polarizations of wireless signals atfrequencies greater than about 100 GHz in accordance with someembodiments.

FIG. 10 is a circuit diagram of an illustrative electronic device havinga Stokes vector receiver for receiving multiple polarizations ofwireless signals at frequencies greater than about 100 GHz in accordancewith some embodiments.

FIG. 11 is a flow chart of illustrative steps that may be performed by atransmitting device and a receiving device for mitigating transmissionimpairments associated with the transmission of multiple polarizationsof wireless signals at frequencies greater than about 100 GHz inaccordance with some embodiments.

DETAILED DESCRIPTION

Electronic device 10 of FIG. 1 (sometimes referred to herein aselectro-optical device 10) may be a computing device such as a laptopcomputer, a desktop computer, a computer monitor containing an embeddedcomputer, a tablet computer, a cellular telephone, a media player, orother handheld or portable electronic device, a smaller device such as awristwatch device, a pendant device, a headphone or earpiece device, adevice embedded in eyeglasses, goggles, or other equipment worn on auser's head, or other wearable or miniature device, a television, acomputer display that does not contain an embedded computer, a gamingdevice, a navigation device, an embedded system such as a system inwhich electronic equipment with a display is mounted in a kiosk orautomobile, a wireless internet-connected voice-controlled speaker, ahome entertainment device, a remote control device, a gaming controller,a peripheral user input device, a wireless base station or access point,equipment that implements the functionality of two or more of thesedevices, or other electronic equipment.

As shown in the functional block diagram of FIG. 1 , device 10 mayinclude components located on or within an electronic device housingsuch as housing 12. Housing 12, which may sometimes be referred to as acase, may be formed of plastic, glass, ceramics, fiber composites, metal(e.g., stainless steel, aluminum, metal alloys, etc.), other suitablematerials, or a combination of these materials. In some situations,parts or all of housing 12 may be formed from dielectric or otherlow-conductivity material (e.g., glass, ceramic, plastic, sapphire,etc.). In other situations, housing 12 or at least some of thestructures that make up housing 12 may be formed from metal elements.

Device 10 may include control circuitry 14. Control circuitry 14 mayinclude storage such as storage circuitry 16. Storage circuitry 16 mayinclude hard disk drive storage, nonvolatile memory (e.g., flash memoryor other electrically-programmable-read-only memory configured to form asolid-state drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Storage circuitry 16 may include storagethat is integrated within device 10 and/or removable storage media.

Control circuitry 14 may include processing circuitry such as processingcircuitry 18. Processing circuitry 18 may be used to control theoperation of device 10. Processing circuitry 18 may include on one ormore processors, microprocessors, microcontrollers, digital signalprocessors, host processors, baseband processor integrated circuits,application specific integrated circuits, central processing units(CPUs), graphics processing units (GPUs), etc. Control circuitry 14 maybe configured to perform operations in device 10 using hardware (e.g.,dedicated hardware or circuitry), firmware, and/or software. Softwarecode for performing operations in device 10 may be stored on storagecircuitry 16 (e.g., storage circuitry 16 may include non-transitory(tangible) computer readable storage media that stores the softwarecode). The software code may sometimes be referred to as programinstructions, software, data, instructions, or code. Software codestored on storage circuitry 16 may be executed by processing circuitry18.

Control circuitry 14 may be used to run software on device 10 such assatellite navigation applications, internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, emailapplications, media playback applications, operating system functions,etc. To support interactions with external equipment, control circuitry14 may be used in implementing communications protocols. Communicationsprotocols that may be implemented using control circuitry 14 includeinternet protocols, wireless local area network (WLAN) protocols (e.g.,IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols forother short-range wireless communications links such as the Bluetooth®protocol or other wireless personal area network (WPAN) protocols, IEEE802.11ad protocols (e.g., ultra-wideband protocols), cellular telephoneprotocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP Fifth Generation(5G) New Radio (NR) protocols, Sixth Generation (6G) protocols, sub-THzprotocols, THz protocols, etc.), antenna diversity protocols, satellitenavigation system protocols (e.g., global positioning system (GPS)protocols, global navigation satellite system (GLONASS) protocols,etc.), antenna-based spatial ranging protocols, optical communicationsprotocols, or any other desired communications protocols. Eachcommunications protocol may be associated with a corresponding radioaccess technology (RAT) that specifies the physical connectionmethodology used in implementing the protocol.

Device 10 may include input-output circuitry 20. Input-output circuitry20 may include input-output devices 22. Input-output devices 22 may beused to allow data to be supplied to device 10 and to allow data to beprovided from device 10 to external devices. Input-output devices 22 mayinclude user interface devices, data port devices, and otherinput-output components. For example, input-output devices 22 mayinclude touch sensors, displays (e.g., touch-sensitive and/orforce-sensitive displays), light-emitting components such as displayswithout touch sensor capabilities, buttons (mechanical, capacitive,optical, etc.), scrolling wheels, touch pads, key pads, keyboards,microphones, cameras, buttons, speakers, status indicators, audio jacksand other audio port components, digital data port devices, motionsensors (accelerometers, gyroscopes, and/or compasses that detectmotion), capacitance sensors, proximity sensors, magnetic sensors, forcesensors (e.g., force sensors coupled to a display to detect pressureapplied to the display), temperature sensors, etc. In someconfigurations, keyboards, headphones, displays, pointing devices suchas trackpads, mice, and joysticks, and other input-output devices may becoupled to device 10 using wired or wireless connections (e.g., some ofinput-output devices 22 may be peripherals that are coupled to a mainprocessing unit or other portion of device 10 via a wired or wirelesslink).

Input-output circuitry 20 may include wireless circuitry 24 to supportwireless communications. Wireless circuitry 24 (sometimes referred toherein as wireless communications circuitry 24) may include one or moreantennas 30.

Wireless circuitry 24 may also include transceiver circuitry 26.Transceiver circuitry 26 may include transmitter circuitry, receivercircuitry, modulator circuitry, demodulator circuitry (e.g., one or moremodems), radio-frequency circuitry, one or more radios, intermediatefrequency circuitry, optical transmitter circuitry, optical receivercircuitry, optical light sources, other optical components, basebandcircuitry (e.g., one or more baseband processors), amplifier circuitry,clocking circuitry such as one or more local oscillators and/orphase-locked loops, memory, one or more registers, filter circuitry,switching circuitry, analog-to-digital converter (ADC) circuitry,digital-to-analog converter (DAC) circuitry, radio-frequencytransmission lines, optical fibers, and/or any other circuitry fortransmitting and/or receiving wireless signals using antennas 30. Thecomponents of transceiver circuitry 26 may be implemented on oneintegrated circuit, chip, system-on-chip (SOC), die, printed circuitboard, substrate, or package, or the components of transceiver circuitry26 may be distributed across two or more integrated circuits, chips,SOCs, printed circuit boards, substrates, and/or packages.

The example of FIG. 1 is merely illustrative. While control circuitry 14is shown separately from wireless circuitry 24 in the example of FIG. 1for the sake of clarity, wireless circuitry 24 may include processingcircuitry (e.g., one or more processors) that forms a part of processingcircuitry 18 and/or storage circuitry that forms a part of storagecircuitry 16 of control circuitry 14 (e.g., portions of controlcircuitry 14 may be implemented on wireless circuitry 24). As anexample, control circuitry 14 may include baseband circuitry (e.g., oneor more baseband processors), digital control circuitry, analog controlcircuitry, and/or other control circuitry that forms part of wirelesscircuitry 24. The baseband circuitry may, for example, access acommunication protocol stack on control circuitry 14 (e.g., storagecircuitry 20) to: perform user plane functions at a PHY layer, MAClayer, RLC layer, PDCP layer, SDAP layer, and/or PDU layer, and/or toperform control plane functions at the PHY layer, MAC layer, RLC layer,PDCP layer, RRC, layer, and/or non-access stratum layer.

Transceiver circuitry 26 may be coupled to each antenna 30 in wirelesscircuitry 24 over a respective signal path 28. Each signal path 28 mayinclude one or more radio-frequency transmission lines, waveguides,optical fibers, and/or any other desired lines/paths for conveyingwireless signals between transceiver circuitry 26 and antenna 30.Antennas 30 may be formed using any desired antenna structures forconveying wireless signals. For example, antennas 30 may includeantennas with resonating elements that are formed from dipole antennastructures, planar dipole antenna structures (e.g., bowtie antennastructures), slot antenna structures, loop antenna structures, patchantenna structures, inverted-F antenna structures, planar inverted-Fantenna structures, helical antenna structures, monopole antennas,dipoles, hybrids of these designs, etc. Filter circuitry, switchingcircuitry, impedance matching circuitry, and/or other antenna tuningcomponents may be adjusted to adjust the frequency response and wirelessperformance of antennas 30 over time.

If desired, two or more of antennas 30 may be integrated into a phasedantenna array (sometimes referred to herein as a phased array antenna)in which each of the antennas conveys wireless signals with a respectivephase and magnitude that is adjusted over time so the wireless signalsconstructively and destructively interfere to produce (form) a signalbeam in a given pointing direction. The term “convey wireless signals”as used herein means the transmission and/or reception of the wirelesssignals (e.g., for performing unidirectional and/or bidirectionalwireless communications with external wireless communicationsequipment). Antennas 30 may transmit the wireless signals by radiatingthe signals into free space (or to free space through intervening devicestructures such as a dielectric cover layer). Antennas 30 mayadditionally or alternatively receive the wireless signals from freespace (e.g., through intervening devices structures such as a dielectriccover layer). The transmission and reception of wireless signals byantennas 30 each involve the excitation or resonance of antenna currentson an antenna resonating (radiating) element in the antenna by thewireless signals within the frequency band(s) of operation of theantenna.

Transceiver circuitry 26 may use antenna(s) 30 to transmit and/orreceive wireless signals that convey wireless communications databetween device 10 and external wireless communications equipment (e.g.,one or more other devices such as device 10, a wireless access point orbase station, etc.). The wireless communications data may be conveyedbidirectionally or unidirectionally. The wireless communications datamay, for example, include data that has been encoded into correspondingdata packets such as wireless data associated with a telephone call,streaming media content, internet browsing, wireless data associatedwith software applications running on device 10, email messages, etc.

Additionally or alternatively, wireless circuitry 24 may use antenna(s)30 to perform wireless sensing operations. The sensing operations mayallow device 10 to detect (e.g., sense or identify) the presence,location, orientation, and/or velocity (motion) of objects external todevice 10. Control circuitry 14 may use the detected presence, location,orientation, and/or velocity of the external objects to perform anydesired device operations. As examples, control circuitry 14 may use thedetected presence, location, orientation, and/or velocity of theexternal objects to identify a corresponding user input for one or moresoftware applications running on device 10 such as a gesture inputperformed by the user's hand(s) or other body parts or performed by anexternal stylus, gaming controller, head-mounted device, or otherperipheral devices or accessories, to determine when one or moreantennas 30 needs to be disabled or provided with a reduced maximumtransmit power level (e.g., for satisfying regulatory limits onradio-frequency exposure), to determine how to steer (form) aradio-frequency signal beam produced by antennas 30 for wirelesscircuitry 24 (e.g., in scenarios where antennas 30 include a phasedarray of antennas 30), to map or model the environment around device 10(e.g., to produce a software model of the room where device 10 islocated for use by an augmented reality application, gaming application,map application, home design application, engineering application,etc.), to detect the presence of obstacles in the vicinity of (e.g.,around) device 10 or in the direction of motion of the user of device10, etc.

Wireless circuitry 24 may transmit and/or receive wireless signalswithin corresponding frequency bands of the electromagnetic spectrum(sometimes referred to herein as communications bands or simply as“bands”). The frequency bands handled by communications circuitry 26 mayinclude wireless local area network (WLAN) frequency bands (e.g., Wi-Fi®(IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLANband (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or otherWi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network(WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPANcommunications bands, cellular telephone frequency bands (e.g., bandsfrom about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New RadioFrequency Range 1 (FR1) bands below 10 GHz, 5G New Radio Frequency Range2 (FR2) bands between 20 and 60 GHz, etc.), other centimeter ormillimeter wave frequency bands between 10-100 GHz, near-fieldcommunications frequency bands (e.g., at 13.56 MHz), satellitenavigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, aGlobal Navigation Satellite System (GLONASS) band, a BeiDou NavigationSatellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bandsthat operate under the IEEE 802.15.4 protocol and/or otherultra-wideband communications protocols, communications bands under thefamily of 3GPP wireless communications standards, communications bandsunder the IEEE 802.XX family of standards, and/or any other desiredfrequency bands of interest.

Over time, software applications on electronic devices such as device 10have become more and more data intensive. Wireless circuitry on theelectronic devices therefore needs to support data transfer at higherand higher data rates. In general, the data rates supported by thewireless circuitry are proportional to the frequency of the wirelesssignals conveyed by the wireless circuitry (e.g., higher frequencies cansupport higher data rates than lower frequencies). Wireless circuitry 24may convey centimeter and millimeter wave signals to support relativelyhigh data rates (e.g., because centimeter and millimeter wave signalsare at relatively high frequencies between around 10 GHz and 100 GHz).However, the data rates supported by centimeter and millimeter wavesignals may still be insufficient to meet all the data transfer needs ofdevice 10. To support even higher data rates such as data rates up to5-10 Gbps or higher, wireless circuitry 24 may convey wireless signalsat frequencies greater than 100 GHz.

As shown in FIG. 1 , wireless circuitry 24 may transmit wireless signals32 and may receive wireless signals 34 at frequencies greater thanaround 100 GHz. Wireless signals 32 and 34 may sometimes be referred toherein as tremendously high frequency (THF) signals 32 and 34, sub-THzsignals 32 and 34, THz signals 32 and 34, or sub-millimeter wave signals32 and 34. THF signals 32 and 34 may be at sub-THz or THz frequenciessuch as frequencies between 100 GHz and 1 THz, between 100 GHz and 10THz, between 100 GHz and 2 THz, between 200 GHz and 1 THz, between 300GHz and 1 THz, between 300 GHz and 2 THz, between 300 GHz and 10 THz,between 100 GHz and 800 GHz, between 200 GHz and 1.5 THz, etc. (e.g.,within a sub-THz, THz, THF, or sub-millimeter frequency band such as a6G frequency band). The high data rates supported by these frequenciesmay be leveraged by device 10 to perform cellular telephone voice and/ordata communications (e.g., while supporting spatial multiplexing toprovide further data bandwidth), to perform spatial ranging operationssuch as radar operations to detect the presence, location, and/orvelocity of objects external to device 10, to perform automotive sensing(e.g., with enhanced security), to perform health/body monitoring on auser of device 10 or another person, to perform gas or chemicaldetection, to form a high data rate wireless connection between device10 and another device or peripheral device (e.g., to form a high datarate connection between a display driver on device 10 and a display thatdisplays ultra-high resolution video), to form a remote radio head(e.g., a flexible high data rate connection), to form a THF chip-to-chipconnection within device 10 that supports high data rates (e.g., whereone antenna 30 on a first chip in device 10 transmits THF signals 32 toanother antenna 30 on a second chip in device 10), and/or to perform anyother desired high data rate operations.

Space is at a premium within electronic devices such as device 10. Insome scenarios, different antennas 30 are used to transmit THF signals32 than are used to receive THF signals 34. However, handlingtransmission of THF signals 32 and reception of THF signals 34 usingdifferent antennas 30 can consume an excessive amount of space and otherresources within device 10 because two antennas 30 and signal paths 28would be required to handle both transmission and reception. To minimizespace and resource consumption within device 10, the same antenna 30 andsignal path 28 may be used to both transmit THF signals 32 and toreceive THF signals 34. If desired, multiple antennas 30 in wirelesscircuitry 24 may transmit THF signals 32 and may receive THF signals 34.The antennas may be integrated into a phased antenna array thattransmits THF signals 32 and that receives THF signals 34 within acorresponding signal beam oriented in a selected beam pointingdirection.

It can be challenging to incorporate components into wireless circuitry24 that support wireless communications at these high frequencies. Ifdesired, transceiver circuitry 26 and signal paths 28 may includeoptical components that convey optical signals to support thetransmission of THF signals 32 and the reception of THF signals 34 in aspace and resource-efficient manner. The optical signals may be used intransmitting THF signals 32 at THF frequencies and in receiving THFsignals 34 at THF frequencies.

FIG. 2 is a diagram of an illustrative antenna 30 that may be used toboth transmit THF signals 32 and to receive THF signals 34 using opticalsignals. Antenna 30 may include one or more antenna radiating(resonating) elements such as radiating (resonating) element arms 36. Inthe example of FIG. 2 , antenna 30 is a planar dipole antenna (sometimesreferred to as a “bowtie” antenna) having two opposing radiating elementarms 36 (e.g., bowtie arms or dipole arms). This is merely illustrativeand, in general, antenna 30 may be any type of antenna having anydesired antenna radiating element architecture.

As shown in FIG. 2 , antenna 30 includes a photodiode (PD) 42 coupledbetween radiating element arms 36. Electronic devices that includeantennas 30 with photodiodes 42 such as device 10 may sometimes also bereferred to as electro-optical devices (e.g., electro-optical device10). Photodiode 42 may be a programmable photodiode. An example in whichphotodiode 42 is a programmable uni-travelling-carrier photodiode (UTCPD) is described herein as an example. Photodiode 42 may thereforesometimes be referred to herein as UTC PD 42 or programmable UTC PD 42.This is merely illustrative and, in general, photodiode 42 may includeany desired type of adjustable/programmable photodiode or component thatconverts electromagnetic energy at optical frequencies to current at THFfrequencies on radiating element arms 36 and/or vice versa. Eachradiating element arm 36 may, for example, have a first edge at UTC PD42 and a second edge opposite the first edge that is wider than thefirst edge (e.g., in implementations where antenna 30 is a bowtieantenna). Other radiating elements may be used if desired.

UTC PD 42 may have a bias terminal 38 that receives one or more controlsignals V_(BIAS). Control signals V_(BIAS) may include bias voltagesprovided at one or more voltage levels and/or other control signals forcontrolling the operation of UTC PD 42 such as impedance adjustmentcontrol signals for adjusting the output impedance of UTC PD 42. Controlcircuitry 14 (FIG. 1 ) may provide (e.g., apply, supply, assert, etc.)control signals V_(BIAS) at different settings (e.g., values,magnitudes, etc.) to dynamically control (e.g., program or adjust) theoperation of UTC PD 42 over time. For example, control signals V_(BIAS)may be used to control whether antenna 30 transmits THF signals 32 orreceives THF signals 34. When control signals V_(BIAS) include a biasvoltage asserted at a first level or magnitude, antenna 30 may beconfigured to transmit THF signals 32. When control signals V_(BIAS)include a bias voltage asserted at a second level or magnitude, antenna30 may be configured to receive THF signals 34. In the example of FIG. 2, control signals V_(BIAS) include the bias voltage asserted at thefirst level to configure antenna 30 to transmit THF signals 32. Ifdesired, control signals V_(BIAS) may also be adjusted to control thewaveform of the THF signals (e.g., as a squaring function that preservesthe modulation of incident optical signals, a linear function, etc.), toperform gain control on the signals conveyed by antenna 30, and/or toadjust the output impedance of UTC PD 42.

As shown in FIG. 2 , UTC PD 42 may be optically coupled to optical path40. Optical path 40 may include one or more optical fibers orwaveguides. UTC PD 42 may receive optical signals from transceivercircuitry 26 (FIG. 1 ) over optical path 40. The optical signals mayinclude a first optical local oscillator (LO) signal LO1 and a secondoptical local oscillator signal LO2. Optical local oscillator signalsLO1 and LO2 may be generated by light sources in transceiver circuitry26 (FIG. 1 ). Optical local oscillator signals LO1 and LO2 may be atoptical wavelengths (e.g., between 400 nm and 700 nm), ultra-violetwavelengths (e.g., near-ultra-violet or extreme ultravioletwavelengths), and/or infrared wavelengths (e.g., near-infraredwavelengths, mid-infrared wavelengths, or far-infrared wavelengths).Optical local oscillator signal LO2 may be offset in wavelength fromoptical local oscillator signal LO1 by a wavelength offset X. Wavelengthoffset X may be equal to the wavelength of the THF signals conveyed byantenna 30 (e.g., between 100 GHz and 1 THz (1000 GHz), between 100 GHzand 2 THz, between 300 GHz and 800 GHz, between 300 GHz and 1 THz,between 300 and 400 GHz, etc.).

During signal transmission, wireless data (e.g., wireless data packets,symbols, frames, etc.) may be modulated onto optical local oscillatorsignal LO2 to produce modulated optical local oscillator signal LO2′. Ifdesired, optical local oscillator signal LO1 may be provided with anoptical phase shift S. Optical path 40 may illuminate UTC PD 42 withoptical local oscillator signal LO1 (plus the optical phase shift S whenapplied) and modulated optical local oscillator signal LO2′. If desired,lenses or other optical components may be interposed between opticalpath 40 and UTC PD 42 to help focus the optical local oscillator signalsonto UTC PD 42.

UTC PD 42 may convert optical local oscillator signal LO1 and modulatedlocal oscillator signal LO2′ (e.g., beats between the two optical localoscillator signals) into antenna currents that run along the perimeterof radiating element arms 36. The frequency of the antenna currents isequal to the frequency difference between local oscillator signal LO1and modulated local oscillator signal LO2′. The antenna currents mayradiate (transmit) THF signals 32 into free space. Control signalV_(BIAS) may control UTC PD 42 to convert the optical local oscillatorsignals into antenna currents on radiating element arms 36 whilepreserving the modulation and thus the wireless data on modulated localoscillator signal LO2′ (e.g., by applying a squaring function to thesignals). THF signals 32 will thereby carry the modulated wireless datafor reception and demodulation by external wireless communicationsequipment.

FIG. 3 is a diagram showing how antenna 30 may receive THF signals 34(e.g., after changing the setting of control signals V_(BIAS) into areception state from the transmission state of FIG. 2 ). As shown inFIG. 3 , THF signals 34 may be incident upon antenna radiating elementarms 36. The incident THF signals 34 may produce antenna currents thatflow around the perimeter of radiating element arms 36. UTC PD 42 mayuse optical local oscillator signal LO1 (plus the optical phase shift Swhen applied), optical local oscillator signal LO2 (e.g., withoutmodulation), and control signals V_(BIAS) (e.g., a bias voltage assertedat the second level) to convert the received THF signals 34 intointermediate frequency signals SIGIF that are output onto intermediatefrequency signal path 44.

The frequency of intermediate frequency signals SIGIF may be equal tothe frequency of THF signals 34 minus the difference between thefrequency of optical local oscillator signal LO1 and the frequency ofoptical local oscillator signal LO2. As an example, intermediatefrequency signals SIGIF may be at lower frequencies than THF signals 32and 34 such as centimeter or millimeter wave frequencies between 10 GHzand 100 GHz, between 30 GHz and 80 GHz, around 60 GHz, etc. If desired,transceiver circuitry 26 (FIG. 1 ) may change the frequency of opticallocal oscillator signal LO1 and/or optical local oscillator signal LO2when switching from transmission to reception or vice versa. UTC PD 42may preserve the data modulation of THF signals 34 in intermediatesignals SIGIF. A receiver in transceiver circuitry 26 (FIG. 1 ) maydemodulate intermediate frequency signals SIGIF (e.g., after furtherdownconversion) to recover the wireless data from THF signals 34. Inanother example, wireless circuitry 24 may convert intermediatefrequency signals SIGIF to the optical domain before recovering thewireless data. In yet another example, intermediate frequency signalpath 44 may be omitted and UTC PD 42 may convert THF signals 34 into theoptical domain for subsequent demodulation and data recovery (e.g., in asideband of the optical signal).

The antenna 30 of FIGS. 2 and 3 may support transmission of THF signals32 and reception of THF signals 34 with a given polarization (e.g., alinear polarization such as a vertical polarization). If desired,wireless circuitry 24 (FIG. 1 ) may include multiple antennas 30 forcovering different polarizations. FIG. 4 is a diagram showing oneexample of how wireless circuitry 24 may include multiple antennas 30for covering different polarizations.

As shown in FIG. 4 , the wireless circuitry may include a first antenna30 such as antenna 30V for covering a first polarization (e.g., a firstlinear polarization such as a vertical polarization) and may include asecond antenna 30 such as antenna 30H for covering a second polarizationdifferent from or orthogonal to the first polarization (e.g., a secondlinear polarization such as a horizontal polarization). Antenna 30V mayhave a UTC PD 42 such as UTC PD 42V coupled between a corresponding pairof radiating element arms 36. Antenna 30H may have a UTC PD 42 such asUTC PD 42H coupled between a corresponding pair of radiating elementarms 36 oriented non-parallel (e.g., orthogonal) to the radiatingelement arms 36 in antenna 30V. This may allow antennas 30V and 30H totransmit THF signals 32 with respective (orthogonal) polarizations andmay allow antennas 30V and 30H to receive THF signals 32 with respective(orthogonal) polarizations.

To minimize space within device 10, antenna 30V may be verticallystacked over or under antenna 30H (e.g., where UTC PD 42V partially orcompletely overlaps UTC PD 42H). In this example, antennas 30V and 30Hmay both be formed on the same substrate such as a rigid or flexibleprinted circuit board. The substrate may include multiple stackeddielectric layers (e.g., layers of ceramic, epoxy, flexible printedcircuit board material, rigid printed circuit board material, etc.). Theradiating element arms 36 in antenna 30V may be formed on a separatelayer of the substrate than the radiating element arms 36 in antenna 30Hor the radiating element arms 36 in antenna 30V may be formed on thesame layer of the substrate as the radiating element arms 36 in antenna30H. UTC PD 42V may be formed on the same layer of the substrate as UTCPD 42H or UTC PD 42V may be formed on a separate layer of the substratethan UTC PD 42H. UTC PD 42V may be formed on the same layer of thesubstrate as the radiating element arms 36 in antenna 30V or may beformed on a separate layer of the substrate as the radiating elementarms 36 in antenna 30V. UTC PD 42H may be formed on the same layer ofthe substrate as the radiating element arms 36 in antenna 30H or may beformed on a separate layer of the substrate as the radiating elementarms 36 in antenna 30H.

If desired, antennas 30 or antennas 30H and 30V of FIG. 4 may beintegrated within a phased antenna array. FIG. 5 is a diagram showingone example of how antennas 30H and 30V may be integrated within aphased antenna array. As shown in FIG. 5 , device 10 may include aphased antenna array 46 of stacked antennas 30H and 30V arranged in arectangular grid of rows and columns. Each of the antennas in phasedantenna array 46 may be formed on the same substrate. This is merelyillustrative. In general, phased antenna array 46 (sometimes referred toas a phased array antenna) may include any desired number of antennas30V and 30H (or non-stacked antennas 30) arranged in any desiredpattern.

Each of the antennas in phased antenna array 46 may be provided with arespective optical phase shift S (FIGS. 2 and 3 ) that configures theantennas to collectively transmit THF signals 32 and/or receive THFsignals 34 that sum to form a signal beam of THF signals in a desiredbeam pointing direction. The beam pointing direction may be selected topoint the signal beam towards external communications equipment, towardsa desired external object, away from an external object, etc.

Phased antenna array 46 may occupy relatively little space within device10. For example, each antenna 30V/30H may have a length 48 (e.g., asmeasured from the end of one radiating element arm to the opposing endof the opposite radiating element arm). Length 48 may be approximatelyequal to one-half the wavelength of THF signals 32 and 34. For example,length 48 may be as small as 0.5 mm or less. Each UTC-PD 42 in phasedantenna array 46 may occupy a lateral area of 100 square microns orless. This may allow phased antenna array 46 to occupy very little areawithin device 10, thereby allowing the phased antenna array to beintegrated within different portions of device 10 while still allowingother space for device components. The examples of FIGS. 2-5 are merelyillustrative and, in general, each antenna may have any desired antennaradiating element architecture.

FIG. 6 is a circuit diagram showing how a given antenna 30 and signalpath 28 (FIG. 1 ) may be used to both transmit THF signals 32 andreceive THF signals 34 based on optical local oscillator signals. In theexample of FIG. 6 , UTC PD 42 converts received THF signals 34 intointermediate frequency signals SIGIF that are then converted to theoptical domain for recovering the wireless data from the received THFsignals.

As shown in FIG. 6 , wireless circuitry 24 may include transceivercircuitry 26 coupled to antenna 30 over signal path 28 (e.g., an opticalsignal path sometimes referred to herein as optical signal path 28). UTCPD 42 may be coupled between the radiating element arm(s) 36 of antenna30 and signal path 28. Transceiver circuitry 26 may include opticalcomponents 68, amplifier circuitry such as power amplifier 76, anddigital-to-analog converter (DAC) 74. Optical components 68 may includean optical receiver such as optical receiver 72 and optical localoscillator (LO) light sources (emitters) 70. LO light sources 70 mayinclude two or more light sources such as laser light sources, laserdiodes, optical phase locked loops, or other optical emitters that emitlight (e.g., optical local oscillator signals LO1 and LO2) at respectivewavelengths. If desired, LO light sources 70 may include a single lightsource and may include optical components for splitting the lightemitted by the light source into different wavelengths. Signal path 28may be coupled to optical components 68 over optical path 66. Opticalpath 66 may include one or more optical fibers and/or waveguides.

Signal path 28 may include an optical splitter such as optical splitter(OS) 54, optical paths such as optical path 64 and optical path 62, anoptical combiner such as optical combiner (OC) 52, and optical path 40.Optical path 62 may be an optical fiber or waveguide. Optical path 64may be an optical fiber or waveguide. Optical splitter 54 may have afirst (e.g., input) port coupled to optical path 66, a second (e.g.,output) port coupled to optical path 62, and a third (e.g., output) portcoupled to optical path 64. Optical path 64 may couple optical splitter54 to a first (e.g., input) port of optical combiner 52. Optical path 62may couple optical splitter 54 to a second (e.g., input) port of opticalcombiner 52. Optical combiner 52 may have a third (e.g., output) portcoupled to optical path 40.

An optical phase shifter such as optical phase shifter 80 may be(optically) interposed on or along optical path 64. An optical modulatorsuch as optical modulator 56 may be (optically) interposed on or alongoptical path 62. Optical modulator 56 may be, for example, aMach-Zehnder modulator (MZM) and may therefore sometimes be referred toherein as MZM 56. MZM 56 includes a first optical arm (branch) 60 and asecond optical arm (branch) 58 interposed in parallel along optical path62. Propagating optical local oscillator signal LO2 along arms 60 and 58of MZM 56 may, in the presence of a voltage signal applied to one orboth arms, allow different optical phase shifts to be imparted on eacharm before recombining the signal at the output of the MZM (e.g., whereoptical phase modulations produced on the arms are converted tointensity modulations at the output of MZM 56). When the voltage appliedto MZM 56 includes wireless data, MZM 56 may modulate the wireless dataonto optical local oscillator signal LO2. If desired, the phase shiftingperformed at MZM 56 may be used to perform beam forming/steering inaddition to or instead of optical phase shifter 80. MZM 56 may receiveone or more bias voltages W_(BIAS) (sometimes referred to herein as biassignals W_(BIAS)) applied to one or both of arms 58 and 60. Controlcircuitry 14 (FIG. 1 ) may provide bias voltage W_(BIAS) with differentmagnitudes to place MZM 56 into different operating modes (e.g.,operating modes that suppress optical carrier signals, operating modesthat do not suppress optical carrier signals, etc.).

Intermediate frequency signal path 44 may couple UTC PD 42 to MZM 56(e.g., arm 60). An amplifier such as low noise amplifier 82 may beinterposed on intermediate frequency signal path 44. Intermediatefrequency signal path 44 may be used to pass intermediate frequencysignals SIGIF from UTC PD 42 to MZM 56. DAC 74 may have an input coupledto up-conversion circuitry, modulator circuitry, and/or basebandcircuitry in a transmitter of transceiver circuitry 26. DAC 74 mayreceive digital data to transmit over antenna 30 and may convert thedigital data to the analog domain (e.g., as data DAT). DAC 74 may havean output coupled to transmit data path 78. Transmit data path 78 maycouple DAC 74 to MZM 56 (e.g., arm 60). Each of the components alongsignal path 28 may allow the same antenna 30 to both transmit THFsignals 32 and receive THF signals 34 (e.g., using the same componentsalong signal path 28), thereby minimizing space and resource consumptionwithin device 10.

LO light sources 70 may produce (emit) optical local oscillator signalsLO1 and LO2 (e.g., at different wavelengths that are separated by thewavelength of THF signals 32/34). Optical components 68 may includelenses, waveguides, optical couplers, optical fibers, and/or otheroptical components that direct the emitted optical local oscillatorsignals LO1 and LO2 towards optical splitter 54 via optical path 66.Optical splitter 54 may split the optical signals on optical path 66(e.g., by wavelength) to output optical local oscillator signal LO1 ontooptical path 64 while outputting optical local oscillator signal LO2onto optical path 62.

Control circuitry 14 (FIG. 1 ) may provide phase control signals CTRL tooptical phase shifter 80. Phase control signals CTRL may control opticalphase shifter 80 to apply optical phase shift S to the optical localoscillator signal LO1 on optical path 64. Phase shift S may be selectedto steer a signal beam of THF signals 32/34 in a desired pointingdirection. Optical phase shifter 80 may pass the phase-shifted opticallocal oscillator signal LO1 (denoted as LO1+S) to optical combiner 52.Signal beam steering is performed in the optical domain (e.g., usingoptical phase shifter 80) rather than in the THF domain because thereare no satisfactory phase shifting circuit components that operate atfrequencies as high as the frequencies of THF signals 32 and 34. Opticalcombiner 52 may receive optical local oscillator signal LO2 over opticalpath 62. Optical combiner 52 may combine optical local oscillatorsignals LO1 and LO2 onto optical path 40, which directs the opticallocal oscillator signals onto UTC PD 42 for use during signaltransmission or reception.

During transmission of THF signals 32, DAC 74 may receive digitalwireless data (e.g., data packets, frames, symbols, etc.) fortransmission over THF signals 32. DAC 74 may convert the digitalwireless data to the analog domain and may output (transmit) the dataonto transmit data path 78 as data DAT (e.g., for transmission viaantenna 30). Power amplifier 76 may amplify data DAT. Transmit data path78 may pass data DAT to MZM 56 (e.g., arm 60). MZM 56 may modulate dataDAT onto optical local oscillator signal LO2 to produce modulatedoptical local oscillator signal LO2′ (e.g., an optical local oscillatorsignal at the frequency/wavelength of optical local oscillator signalLO2 but that is modulated to include the data identified by data DAT).Optical combiner 52 may combine optical local oscillator signal LO1 withmodulated optical local oscillator signal LO2′ at optical path 40.

Optical path 40 may illuminate UTC PD 42 with (using) optical localoscillator signal LO1 (e.g., with the phase shift S applied by opticalphase shifter 80) and modulated optical local oscillator signal LO2′.Control circuitry 14 (FIG. 1 ) may apply a control signal V_(BIAS) toUTC PD 42 that configures antenna 30 for the transmission of THF signals32. UTC PD 42 may convert optical local oscillator signal LO1 andmodulated optical local oscillator signal LO2′ into antenna currents onradiating element arm(s) 36 at the frequency of THF signals 32 (e.g.,while programmed for transmission using control signal V_(BIAS)). Theantenna currents on radiating element arm(s) 36 may radiate THF signals32. The frequency of THF signals 32 is given by the difference infrequency between optical local oscillator signal LO1 and modulatedoptical local oscillator signal LO2′. Control signals V_(BIAS) maycontrol UTC PD 42 to preserve the modulation from modulated opticallocal oscillator signal LO2′ in the radiated THF signals 32. Externalequipment that receives THF signals 32 will thereby be able to extractdata DAT from the THF signals 32 transmitted by antenna 30.

During reception of THF signals 34, MZM 56 does not modulate any dataonto optical local oscillator signal LO2. Optical path 40 thereforeilluminates UTC PD 42 with optical local oscillator signal LO1 (e.g.,with phase shift S) and optical local oscillator signal LO2. Controlcircuitry 14 (FIG. 1 ) may apply a control signal V_(BIAS) (e.g., a biasvoltage) to UTC PD 42 that configures antenna 30 for the receipt of THFsignals 32. UTC PD 42 may use optical local oscillator signals LO1 andLO2 to convert the received THF signals 34 into intermediate frequencysignals SIGIF output onto intermediate frequency signal path 44 (e.g.,while programmed for reception using bias voltage V_(BIAS)).Intermediate frequency signals SIGIF may include the modulated data fromthe received THF signals 34. Low noise amplifier 82 may amplifyintermediate frequency signals SIGIF, which are then provided to MZM 56(e.g., arm 60). MZM 56 may convert intermediate frequency signals SIGIFto the optical domain as optical signals LOrx (e.g., by modulating thedata in intermediate frequency signals SIGIF onto one of the opticallocal oscillator signals) and may pass the optical signals to opticalreceiver 72 in optical components 68, as shown by arrow 63 (e.g., viaoptical paths 62 and 66 or other optical paths). Control circuitry 14(FIG. 1 ) may use optical receiver 72 to convert optical signals LOrx toother formats and to recover (demodulate) the data carried by THFsignals 34 from the optical signals. In this way, the same antenna 30and signal path 28 may be used for both the transmission and receptionof THF signals while also performing beam steering operations.

The example of FIG. 6 in which intermediate frequency signals SIGIF areconverted to the optical domain is merely illustrative. If desired,transceiver circuitry 26 may receive and demodulate intermediatefrequency signals SIGIF without first passing the signals to the opticaldomain. For example, transceiver circuitry 26 may include ananalog-to-digital converter (ADC), intermediate frequency signal path 44may be coupled to an input of the ADC rather than to MZM 56, and the ADCmay convert intermediate frequency signals SIGIF to the digital domain.As another example, intermediate frequency signal path 44 may be omittedand control signals V_(BIAS) may control UTC PD 42 to directly sampleTHF signals 34 with optical local oscillator signals LO1 and LO2 to theoptical domain. As an example, UTC PD 42 may use the received THFsignals 34 and control signals V_(BIAS) to produce an optical signal onoptical path 40. The optical signal may have an optical carrier withsidebands that are separated from the optical carrier by a fixedfrequency offset (e.g., 30-100 GHz, 60 GHz, 50-70 GHz, 10-100 GHz,etc.). The sidebands may be used to carry the modulated data from thereceived THF signals 34. Signal path 28 may direct (propagate) theoptical signal produced by UTC PD 42 to optical receiver 72 in opticalcomponents 68 (e.g., via optical paths 40, 64, 62, 66, 63, and/or otheroptical paths). Control circuitry 14 (FIG. 1 ) may use optical receiver72 to convert the optical signal to other formats and to recover(demodulate) the data carried by THF signals 34 from the optical signal(e.g., from the sidebands of the optical signal).

FIG. 7 is a circuit diagram showing one example of how multiple antennas30 may be integrated into a phased antenna array 88 that conveys THFsignals over a corresponding signal beam. In the example of FIG. 7 ,MZMs 56, intermediate frequency signal paths 44, data paths 78, andoptical receiver 72 of FIG. 6 have been omitted for the sake of clarity.Each of the antennas in phased antenna array 88 may alternatively samplereceived THF signals directly into the optical domain or may passintermediate frequency signals SIGIF to ADCs in transceiver circuitry26.

As shown in FIG. 7 , phased antenna array 88 includes N antennas 30 suchas a first antenna 30-0, a second antenna 30-1, and an Nth antenna30-(N−1). Each of the antennas 30 in phased antenna array 88 may becoupled to optical components 68 via a respective optical signal path(e.g., optical signal path 28 of FIG. 6 ). Each of the N signal pathsmay include a respective optical combiner 52 coupled to the UTC PD 42 ofthe corresponding antenna 30 (e.g., the UTC PD 42 in antenna 30-0 may becoupled to optical combiner 52-0, the UTC PD 42 in antenna 30-1 may becoupled to optical combiner 52-1, the UTC PD 42 in antenna 30-(N−1) maybe coupled to optical combiner 52-(N−1), etc.). Each of the N signalpaths may also include a respective optical path 62 and a respectiveoptical path 64 coupled to the corresponding optical combiner 52 (e.g.,optical paths 64-0 and 62-0 may be coupled to optical combiner 52-0,optical paths 64-1 and 62-1 may be coupled to optical combiner 52-1,optical paths 64-(N−1) and 62-(N−1) may be coupled to optical combiner52-(N−1), etc.).

Optical components 68 may include LO light sources 70 such as a first LOlight source 70A and a second LO light source 70B. The optical signalpaths for each of the antennas 30 in phased antenna array 88 may shareone or more optical splitters 54 such as a first optical splitter 54Aand a second optical splitter 54B. LO light source 70A may generate(e.g., produce, emit, transmit, etc.) first optical local oscillatorsignal LO1 and may provide first optical local oscillator signal LO1 tooptical splitter 54A via optical path 66A. Optical splitter 54A maydistribute first optical local oscillator signal LO1 to each of the UTCPDs 42 in phased antenna array 88 over optical paths 64 (e.g., opticalpaths 64-0, 64-1, 64-(N−1), etc.). Similarly, LO light source 70B maygenerate (e.g., produce, emit, transmit, etc.) second optical localoscillator signal LO2 and may provide second optical local oscillatorsignal LO2 to optical splitter 54B via optical path 66B. Opticalsplitter 54B may distribute second optical local oscillator signal LO2to each of the UTC PDs 42 in phased antenna array 88 over optical paths62 (e.g., optical paths 62-0, 62-1, 62-(N−1), etc.).

A respective optical phase shifter 80 may be interposed along (on) eachoptical path 64 (e.g., a first optical phase shifter 80-0 may beinterposed along optical path 64-0, a second optical phase shifter 80-1may be interposed along optical path 64-1, an Nth optical phase shifter80-(N−1) may be interposed along optical path 64-(N−1), etc.). Eachoptical phase shifter 80 may receive a control signal CTRL that controlsthe phase S provided to optical local oscillator signal LO1 by thatoptical phase shifter (e.g., first optical phase shifter 80-0 may impartan optical phase shift of zero degrees/radians to the optical localoscillator signal LO1 provided to antenna 30-0, second optical phaseshifter 80-1 may impart an optical phase shift of Δϕ to the opticallocal oscillator signal LO1 provided to antenna 30-1, Nth optical phaseshifter 80-(N−1) may impart an optical phase shift of (N−1)Δϕ to theoptical local oscillator signal LO1 provided to antenna 30-(N−1), etc.).By adjusting the phase S imparted by each of the N optical phaseshifters 80, control circuitry 14 (FIG. 1 ) may control each of theantennas 30 in phased antenna array 88 to transmit THF signals 32 and/orto receive THF signals 34 within a formed signal beam 83. Signal beam 83may be oriented in a particular beam pointing direction (angle) 84(e.g., the direction of peak gain of signal beam 83). The THF signalsconveyed by phased antenna array 88 may have wavefronts 86 that areorthogonal to beam pointing direction 84. Control circuitry 14 mayadjust beam pointing direction 84 over time to point towards externalcommunications equipment or an external object or to point away fromexternal objects, as examples.

Phased antenna array 88 may be operable in an active mode in which thearray transmits and/or receives THF signals using optical localoscillator signals LO1 and LO2 (e.g., using phase shifts provided toeach antenna element to steer signal beam 83). If desired, phasedantenna array 88 may also be operable in a passive mode in which thearray does not transmit or receive THF signals. Instead, in the passivemode, phased antenna array 88 may be configured to form a passivereflector that reflects THF signals or other electromagnetic wavesincident upon device 10. In the passive mode, the UTC PDs 42 in phasedantenna array 88 are not illuminated by optical local oscillator signalsLO1 and LO2 and transceiver circuitry 26 performs nomodulation/demodulation, mixing, filtering, detection, modulation,and/or amplifying of the incident THF signals.

Antenna radiating element arm(s) 36 and UTC PD 42 (FIG. 6 ) maysometimes be referred to herein collectively as access point (AP) 45(e.g., a THF access point). In some implementations, a single accesspoint 45 is used to communicate with a single external device (e.g.,another device such as device 10, a wireless base station or accesspoint, or other wireless (THF) communications equipment). If desired,transceiver 26 may use multiple access points distributed across one ormore locations to concurrently communicate with one or more externaldevices over one or more streams of wireless signals (e.g., THF signals32 and 34 of FIG. 1 ).

To maximize the overall data rate and/or flexibility of THFcommunications performed using device 10, wireless circuitry 24 mayconvey THF signals using multiple electromagnetic polarizations such asa first polarization and a second polarization that is different from(e.g., orthogonal to) the first polarization. Each polarization may, forexample, be used to concurrently convey respective streams of wirelessdata. FIG. 8 is a diagram showing one example of how device 10 mayconvey THF signals using multiple electromagnetic polarizations.

As shown in FIG. 8 , wireless communications system 95 (sometimesreferred to herein as THF system 95, wireless system 95, communicationssystem 95, or simply as system 95) may include one or more access pointssuch as access point 45. Access point 45 may include at least onedual-polarization antenna 94. Dual-polarization antenna 94 may, forexample, include overlapping antennas 30V and 30H having orthogonalradiating element arms (e.g., bow tie antennas as shown in FIG. 4 ).Antennas 30V and 3011 may be fed using respective UTC PDs 42 in accesspoint 45, for example. Antenna 3011 may transmit THF signals with afirst polarization such as THF signals 32H whereas antenna 30V transmitsTHF signals with a second polarization orthogonal to the firstpolarization such as THF signals 32V.

In the example of FIG. 8 , THF signals 32H have a first linearpolarization (e.g., a horizontal polarization) whereas THF signals 32Vhave a second linear polarization orthogonal to the first linearpolarization (e.g., a vertical polarization). This is merelyillustrative. In general, THF signals 32H and 32V may have any desiredpolarizations. THF signals 32H and 32V need not be linearly polarizedand, if desired, other polarizations such as circular or ellipticalpolarizations may be used. While THF signals 3211 and antenna 30H aresometimes referred to herein as “horizontally polarized” or areotherwise denoted using the letter H, the angle of the correspondingelectric field may be oriented in any desired direction. Similarly,while THF signals 32V and antenna 30V are sometimes referred to hereinas “vertically polarized” or are otherwise denoted using the letter V,the angle of the corresponding electric field may be oriented in anydesired direction (e.g., orthogonal to the direction of the“horizontally polarized” signals).

Wireless communications system 95 may also include a centralized opticalcontroller such as central optical controller 90. Central opticalcontroller 90 may sometimes also be referred to herein as central office90, central chip 90, optical controller 90, or optical processor 90.Central optical controller 90 may include control circuitry such ascontrol circuitry 14 of FIG. 1 . The components of wireless circuitry 24of FIG. 6 may be distributed between access points 45 and centraloptical controller 90 of FIG. 8 . For example, central opticalcontroller 90 may include transceiver 26 and signal path 28 of FIG. 6 .Central optical controller 90 may be communicably coupled to accesspoint 45 over an optical signal path such as optical path 92. Opticalpath 92 may include one or more optical fibers and/or waveguides.

Central optical controller 90 may be co-located with access point 45 ormay be disposed at a location separated from access point 45. Forexample, central optical controller 90, optical path 92, and accesspoint 45 may all be enclosed within an electronic device housing such ashousing 102 (e.g., a housing such as housing 12 of FIG. 1 ). Whenconfigured in this way, central optical controller 90, optical path 92,and access point 45 may all form components of a corresponding device10. As another example, central optical controller 90 may be enclosedwithin a first housing such as housing 96 (e.g., a housing such ashousing 12 of FIG. 1 ) whereas access point 45 is enclosed within asecond housing 100 (e.g., a housing such as housing 12 of FIG. 1 ). Whenconfigured in this way, central optical controller 90 may be locatedwithin a first device 10 whereas access point 45 is located within asecond device 10.

In other words, wireless communications system 95 may be located withina single device 10 or may be distributed across multiple devices 10. Inexamples where the components of wireless communications system 95 arelocated within a single device 10, access point 45 may be separated fromor co-located with central optical controller 90 within the device andoptical path 92 may have a length on the order of inches, centimeters,or meters. In examples where the components of wireless communicationssystem 95 are located within different devices 10, central opticalcontroller 90 may be located in the same room or a different room of thesame building or a different building as access point 45 or may belocated in a different geographic region from access point 45 (e.g.,optical path 92 may be as long as a few km, dozens of km, hundreds ofkm, or thousands of km in length). If desired, optical path 92 mayinclude multiple optical fibers that are coupled together in seriesusing optical couplers, optical boosters/amplifiers, optical relays,etc.

Central optical controller 90 may generate optical signals (e.g.,optical local oscillator signals) for access point 45. Central opticalcontroller 90 may transmit the optical signals over optical path 92.Access point 45 may transmit wireless signals 3211 and 32V using theoptical signals. Access point 45 may transmit THF signals 32H and 32V toone or more external devices such as external device 98. The UTC PD 42coupled to antenna 30V may transmit THF signals 32V using a pair ofoptical signals received over optical path 92 (e.g., where the frequencyof THF signals 32V is given by the difference in frequency between thepair of optical signals). Similarly, the UTC PD 42 coupled to antenna30H may transmit THF signals 32H using a pair of optical signalsreceived over optical path 92 (e.g., where the frequency of THF signals32H is given by the difference in frequency between the pair of opticalsignals). External device 98 may be another device such as device 10, awireless base station or access point, or other wireless (THF)communications equipment, for example. While FIG. 8 illustrates thetransmission of THF signals 32H and 32V, wireless communications system95 may additionally or alternatively receive THF signals 34 (FIG. 1 )from external device 98 in one or more (e.g., orthogonal) polarizations.

The fiber and radio resources in wireless communications system 95should be as tightly coupled as possible. Coupling the fiber and radioparameters (e.g., bandwidth, modulation order, polarization, symbolrate, etc.) as much as possible may minimize the resources required ataccess point 45, where only minimal processing of the optical signalsfrom central optical controller 90 towards THF frequencies would berequired. In a simplest case, an optical polarization plane may befrequency shifted to a linearly polarized THF signal. This may avoid anydemodulation and remodulation within access point 45. As a consequence,the optical fiber channel and the THF (radio) transmission channel maybe viewed as a combined overall channel.

Conveying THF signals with multiple polarizations can raise manychallenges to efficient wireless communications between external device98 and wireless communications system 95. For example, external device98 may be able to coherently demodulate the separate streams of wirelessdata in THF signals 32H and 32V when the antennas on external device 98for conveying THF signals in each polarization are aligned with theantennas on wireless communications system 95 that transmitted THFsignals 32H and 32V, when external device 98 does not move or rotatewith respect to wireless communications system 95, and when wirelesscommunications system 95 does not move or rotate with respect toexternal device 98.

In practice, wireless communications system 95 and/or external device 98will move and/or rotate frequently over time. Wireless communicationssystem 95 may not have knowledge at any given moment of the preciseorientation and position of external device 98 with respect to wirelesscommunications system 95. Similarly, external device 98 may not haveknowledge at any given moment of the precise orientation and position ofwireless communications system 95. As such, if care is not taken, it canbe difficult for external device 98 to demodulate the different wirelessdata streams in THF signals 32H and 32V properly and coherently (e.g.,due to the misalignment and/or changing alignment between wirelesscommunications system 95 and external device 98).

In addition, polarization dispersion in the optical fibers of wirelesscommunications system 95 (e.g., optical path 92) and radio-frequencytransmission/polarization impairments (e.g., in access point 45) canfurther limit the ability of external device 98 to coherently demodulatethe different wireless data streams in THF signals 32H and 32V. Tomitigate these issues, wireless communications system 95 and externaldevice 98 may use THF signals 32H and 32V to estimate and mitigate themisalignment between external device 98 and wireless communicationssystem 95 and to mitigate transmission impairments within wirelesscommunications system 95.

To further illustrate the transmission impairments within wirelesscommunications system 95, consider a system model for the most dominanterror signals in a dual-polarization coherent optical fiber system. Inthis model, the transmission impairments generally include chromaticdispersion (CD) and polarization effects such as polarization-modedispersion (PMD). PMD is modeled as polarization rotation, representedby a unitary matrix and differential group delay (DGD) between theorthogonal polarization tributaries. Amplified spontaneous emission(ASE) from erbium-doped fiber amplifiers may be modeled as additivewhite Gaussian noise (AWGN) for the optical field. Nonlinear distortionsinduced through transmission over the optical fiber and transmit (TX)in-phase quadrature-phase (I/Q) imbalance are disregarded. Thetransmitted signal of each polarization is multiplexed and transmittedover the optical fiber (e.g., optical path 92). The optical linear fieldimpairments can be modeled using equation 1.

H(ω)=J·D(ω)·C(z,ω)   (1)

In equation 1, ω is angular frequency, z is propagation distance, J is aJones matrix representation of a random polarization rotation withrandom phase shifts between transmit and receiver axes (e.g., as givenby equation 2), D(ω) is a matrix that represents the PMD-induceddifferential group delay between both polarization waves, whose valuesgenerally range between 1 and 100 ps (e.g., as given by equation 3), andC(z,ω) corresponds to the frequency response of chromatic dispersion(e.g., as given by equation 4).

$\begin{matrix}{J = \begin{pmatrix}{\cos\alpha} & {e^{{- j}\theta}\sin\alpha} \\{{- e^{{- j}0}}\sin\alpha} & {\cos\alpha}\end{pmatrix}} & (2)\end{matrix}$

In equation 2, α is the azimuth rotation angle and θ is the elevationrotation angle that can make the signal state of polarization sweep overthe entire Poincaré sphere, and j is the square root of negative one.

$\begin{matrix}{{D(\omega)} = \begin{pmatrix}e^{j\omega\tau/2} & 0 \\0 & e^{{- j}\omega\tau/2}\end{pmatrix}} & (2)\end{matrix}$ $\begin{matrix}{{C(\omega)} = {e^{\frac{{- j}\lambda^{2}{Dz}}{4\pi c}}\omega^{2}}} & (4)\end{matrix}$

In equation 4, λ is the central wavelength of the transmitted opticalwave, c is the speed of light in a vacuum, and D is the fiber chromaticdispersion coefficient. Polarization dependent loss (PDL) is omittedfrom the model.

Additional transmission impairments are also considered, as thefiber-impaired signal is directly transferred to THF and experiencesadditional radio transmission impairments. Such impairments includemisalignment (rotation) between wireless communications system 95 andexternal device 98. Assuming a simplest case that only accounts for lineof sign (LOS) between wireless communications system 95 and externaldevice 98, rotation of external device 98 (e.g., the mobile receiver) isconsidered in the polarization plane. In the model, the transmitpolarization direction and the receiver polarization direction are eachprojected onto a projection plane. In the projection plane, theprojected receiver polarization direction is oriented at a rotationangle α with respect to a vector in the projection plane that isorthogonal to the transmit polarization direction as projected into theprojection plane (assuming that the transmitter and the receiver arearranged on the optical axis so the electric field is perpendicular tothe axis). This results in a Jones matrix M(ϑ) as given by equation 5.

$\begin{matrix}{{M(\vartheta)} = \begin{pmatrix}{\cos\vartheta} & {\sin\vartheta} \\{{- \sin}\vartheta} & {\cos\vartheta}\end{pmatrix}} & (5)\end{matrix}$

Transmission impairments associated with UTC PD 42 and the antennas thatconvey THF signals 32H and 32V are generally on the order of −20 dB fromone polarization to another. As such, these impairments can be omittedfrom the model. Given each of these impairments, optical fiber and THFpolarization impairments can be modeled/represented more simply usingthe matrix H(ω) given by equation 6, which characterizes the overallimpairment response associated with transmission of THF signals 32H and32V by wireless communications system 95 to external device 98 (e.g.,taking into account impairments in the optical domain at wirelesscommunications system 95, in the THF domain at wireless communicationssystem 95, and in the THF domain as given by the rotation/misalignmentof wireless communications system 95 with respect to external device98).

H(ω)=J·D(ω)·C(z,ω)·M(ϑ)   (6)

The transmitting device (e.g., wireless communications system 95) andthe receiving device (e.g., external device 98) may be configured tomitigate these transmission impairments to maximize the communicationsefficiency of the system. FIG. 9 is a circuit diagram showing oneexample of how central optical controller 90 of FIG. 8 may transmitoptical signals to access point 45.

As shown in FIG. 9 , central optical controller 90 may include LO lightsources such as light sources 120 and 122 (e.g., light sources such aslight sources 70 of FIG. 6 or light sources 70A and 70B of FIG. 7 ).Light sources 120 and 122 may include light-emitting diodes or laserlight sources, as examples. Light source 120 may be coupled to a firstoptical combiner (OC) 130 over optical path 118 (e.g., one or moreoptical fibers, waveguides, etc.). Light source 120 may also be coupledto a second optical combiner (OC) 136 over optical path 116 (e.g., oneor more optical fibers, waveguides, etc.). Light source 122 may also becoupled to optical combiners 130 and 136 over optical path 134 (e.g.,one or more optical fibers, waveguides, etc.).

Central optical controller 90 may include an optical modulator such asoptical modulator 124 interposed along optical path 118. Opticalmodulator 124 may, for example, include a first optical branch 126 and asecond optical branch 128 and may include MZMs 58 interposed on eachoptical branch. Optical modulator 124 may receive wireless data DAT fortransmission. Wireless data DAT may include, for example, I/Q data(e.g., where in-phase data DAT(I) is provided to the MZM 58 on opticalbranch 126 and quadrature-phase data DAT(Q) is provided to the MZM 58 onoptical branch 128). The output of optical combiners 130 and 136 may becoupled to the input of polarization combiner 132. The output ofpolarization combiner 132 may be coupled to optical path 92.

During wireless transmission, light source 120 may emit light (e.g., LOsignals) on optical paths 118 and 116 at an optical frequency such asfrequency f_0. Optical structures in central optical controller 90 mayconfigure the light at frequency f_0 emitted onto optical path 118 toexhibit a first polarization (e.g., a vertical linear polarization V)and may configure the light at frequency f_0 emitted onto optical path116 to exhibit a second polarization that is different from (e.g.,orthogonal to) the first polarization (e.g., a horizontal linearpolarization H).

Central optical controller 90 may use optical modulator 124 to modulatea signal (e.g., wireless data DAT) onto the vertically polarized lightat frequency f_0 emitted onto optical path 118 by light source 120 toproduce (generate) a vertically (V) polarized modulated signal such asmodulated signal S(V) (e.g., a modulated signal on a carrier atfrequency f_0). The light emitted onto optical path 116 is un-modulatedand is therefore referred to herein as a horizontally (H) polarizedunmodulated carrier C(H). At the same time, light source 122 may emit anoptical local oscillator signal at frequency f LO onto optical path 134.

Optical combiner 130 may combine the optical local oscillator signal atfrequency f LO with modulated signal S(V) to produce verticallypolarized combined signal S′(V) (e.g., a dual tone signal pair where onetone is modulated with wireless data DAT). Graph 110 of FIG. 9 plotsvertically polarized combined signal S′(V) in power (P) as a function offrequency (F). As shown by graph 110, vertically polarized combinedsignal S′(V) includes an unmodulated spectral line (peak) at frequency fLO (e.g., from the optical local oscillator signal emitted by lightsource 122) and a modulated signal (e.g., as produced by opticalmodulator 124) on a carrier at frequency f_0 (e.g., as produced by lightsource 120). Frequency f LO is separated from frequency f_0 by frequencygap 114. Frequency gap 114 corresponds to the frequency of the wirelesssignals conveyed by access point 45 (FIG. 8 ) using vertically polarizedcombined signal S′(V). Frequency gap 114 may be, for example 25-1000GHz.

Similarly, optical combiner 136 may combine the optical local oscillatorat frequency f_LO with unmodulated carrier C(H) to produce horizontallypolarized combined signal C′(H) (e.g., a dual tone signal pair whereboth tones are unmodulated). Graph 112 of FIG. 9 plots horizontallypolarized combined signal C′(H). As shown by graph 112, horizontallypolarized combined signal C′(H) includes a first unmodulated spectralline (peak) at frequency f_LO (e.g., from the optical local oscillatorsignal emitted by light source 122) and a second unmodulated spectralline (peak) at frequency f_0 (e.g., as produced by light source 120).Polarization combiner 132 may combine the optical signals of eachpolarization (e.g., may combine the vertically polarized combined signalS′(V) and the horizontally polarized combined signal C′(H)) and mayoutput the optical signals on optical path 92.

Access point 45 (FIG. 8 ) may receive combined signals S′(V) and C′(H)over optical path 92. Access point 45 may include a polarizationsplitter that separates combined signal S′(V) from combined signalC′(H). Access point 45 may include a first UTC PD 42 coupled to antenna30V in dual-polarization antenna 94 (FIG. 8 ) that is illuminated usingcombined signal S′(V) to cause antenna 30V to convey verticallypolarized THF signals (e.g., THF signals 32V of FIG. 8 ). Access point45 may include a second UTC PD 42 coupled to antenna 30H indual-polarization antenna 94 (FIG. 8 ) that is illuminated usingcombined signal C′(H) to cause antenna 30H to convey horizontallypolarized THF signals (e.g., THF signals 32H of FIG. 8 ). If desired,access point 45 may include multiple dual-polarization antennas 94(e.g., in a phased antenna array as shown in FIG. 7 ) to convey THFsignals 32H and 32V in signal beams oriented in a selected beam pointingdirection. The example of FIG. 9 is merely illustrative. If desired,central optical controller 90 may use other transmit signal definitionsto produce optical signals for controlling antennas 30V and 30H inaccess point 45 to convey THF signals of any desired polarizations.

FIG. 10 is a circuit diagram showing one example of how external device98 of FIG. 8 may receive and process the THF signals 32V and 32Htransmitted by wireless communications system 95 (e.g., while mitigatingtransmission impairments associated with communicating using THF signalsof different polarizations). In the example of FIG. 10 , external device98 is an electronic device such as device 10.

As shown in FIG. 10 , device 10 may include a dual-polarization antennasuch as dual-polarization antenna 140. While only a singledual-polarization antenna 140 is illustrated in FIG. 10 for the sake ofclarity, device 10 may include a phased antenna array ofdual-polarization antennas 140 if desired. Dual-polarization antenna 140may include antenna 32V for conveying vertically polarized THF signalsand antenna 32H for conveying horizontally polarized THF signals. Thisis merely illustrative and, in general, dual-polarization antenna 140may convey THF signals with any desired polarizations.

Dual-polarization antenna 140 may be coupled to a first photodiode suchas photodiode 144 and to a second photodiode such as photodiode 142(e.g., UTC photodiodes such as UTC photodiode 42 of FIG. 6 ). Device 10may include a light source 146 (e.g., a light source in light sources 70of FIG. 6 ) that illuminates photodiodes 142 and 144 using optical localoscillator signal LO3. Light source 146 may include, for example, avertical cavity surface emitting laser (VCSEL). Optical local oscillatorsignal LO3 may be at a carrier frequency of combined signals S′(V) andC′(H) and thus THF signals 32H/32V (e.g., frequency f_0 of light source120 in central optical controller 90 of FIG. 9 ).

Antenna 32V may receive THF signals 32V from wireless communicationssystem 95 (FIG. 8 ) as vertically polarized receive signals RXTHF(V)(e.g., at a frequency equal to frequency gap 114 of FIG. 9 ). Antenna32V may pass vertically polarized receive signals RXTHF(V) to photodiode142. If desired, one or more amplifiers (e.g., low noise amplifiers) mayamplify vertically polarized receive signals RXTHF(V) prior totransmission to photodiode 144. Similarly, antenna 32H may receive THFsignals 32H from wireless communications system 95 as horizontallypolarized receive signals RXTHF(H) (e.g., at a frequency equal tofrequency gap 114 of FIG. 9 ). Antenna 32H may pass horizontallypolarized receive signals RXTHF(H) to photodiode 144. If desired, one ormore amplifiers (e.g., low noise amplifiers) may amplify horizontallypolarized receive signals RXTHF(H) prior to transmission to photodiode142.

Photodiode 144 may use optical local oscillator signal LO3 to upconverthorizontally polarized receive signals RXTHF(H) to an optical frequencyas horizontally polarized optical signals RXOPT(H). Similarly,photodiode 142 may use optical local oscillator signal LO3 to upconvertvertically polarized receive signals RXTHF(V) to an optical frequency asvertically polarized optical signals RXOPT(V). In other words,photodiodes 144 and 142 may convert the received signals from the THFdomain to the optical domain.

As shown in FIG. 10 , the transceiver circuitry in device 10 may includea Stokes vector receiver such as Stokes vector receiver (SVR) 160. SVR160 may have two or more input ports (terminals) such as input ports152. SVR 160 may also have three or more output ports (terminals) suchas output ports 154. A first input port 152 of SVR 160 may be coupled tophotodiode 144 over optical path 150 (e.g., one or more optical fibersand/or waveguides). A second input port 152 of SVR 160 may be coupled tophotodiode 142 over optical path 148 (e.g., one or more optical fibersand/or waveguides). Photodiode 144 may emit horizontally polarizedoptical signals RXOPT(H) on optical path 150 and SVR 160 may receivehorizontally polarized optical signals RXOPT(H) over its first inputport 152. Photodiode 142 may emit vertically polarized optical signalsRXOPT(V) on optical path 148 and SVR 160 may receive verticallypolarized optical signals RXOPT(V) over its second input port 152.

SVR 160 may include a first optical coupler such as optical coupler 158and a second optical coupler such as optical coupler 162 (e.g., opticalsplitters and optionally optical combiners). Optical coupler 158 may becoupled to the first input port 152. Optical coupler 162 may be coupledto the second input port 152. SVR 160 may also include a downconvertingmixing device such as mixing device 156. Mixing device 156 may be, forexample, a 90-degree optical hybrid mixing device such as a photonichomodyne receiver (e.g., a direct conversion homodyne mixing device).

SVR 160 may include a set of photodetectors (e.g., balancedphotodetectors) such as photodiodes 164, 166, and 168. Photodiode 164may be optically coupled to optical coupler 158 and optical coupler 162.Photodiode 168 may be optically coupled to the output of mixing device156. Photodiode 166 may be optically coupled to the output of mixingdevice 166. Photodiodes 164, 166, and 168 may also be coupled torespective output ports 154 of SVR 160. Mixing device 156 may haveinputs coupled to optical couplers 158 and 162.

During signal reception, optical coupler 158 may provide horizontallypolarized optical signal RXOPT(H) to photodiode 164 and the input ofmixing device 156. Optical coupler 162 may provide vertically polarizedoptical signal RXOPT(V) to photodiode 164 and the input of mixing device156. Mixing device 156 may perform homodyne mixing on horizontallypolarized optical signal RXOPT(H) and vertically polarized opticalsignal RXOPT(V) that downconverts the signals and may provide (output)optical signals to photodiodes 166 and 168.

SVR 160 may output a Stokes vector SV on output ports 154. Each outputport 154 may output a respective vector element from Stokes vector SV.For example, photodiode 164 may be illuminated using verticallypolarized optical signal RXOPT(V) and horizontally polarized opticalsignal RXOPT(H) to produce vector element S₁ of stokes vector SV on afirst output port 154 of SVR 160. Similarly, photodiode 168 may beilluminated using first outputs of mixing device 156 to produce vectorelement S₂ of stokes vector SV on a second output port 154 of SVR 160and photodiode 166 may be illuminated using second outputs of mixingdevice 156 to produce vector element S₃ of Stokes vector SV on a thirdoutput port 154 of SVR 160. In other words, Stokes vector SV may berepresented by the vector [S₁, S₂, S₃]^(T), where T is the transposeoperator. This example is merely illustrative. Stokes vector SV may havemore than three elements (e.g., four elements) and SVR 160 may have morethan three output ports 154 (e.g., four output ports). Stokes vector SVmay include single-ended or differential signals. Other SVRarchitectures may be used if desired.

The THF signals 32H and 32V received at device 10 may be expressed by aJones vector J=[S, C]^(T), where S is the modulated signal fromvertically polarized combined signal S′(V) and C is the unmodulatedcarrier from horizontally polarized combined signal C′(H) (FIG. 9 ).Assuming no polarization rotation (e.g., perfect alignment) betweenwireless communications system 95 and device 10 of FIG. 10 , the Jonesvector would appear like the ideal Stokes Vector SV when output by SVR160. In other words, in the absence of polarization rotation, SVR 160may output a Stokes vector SV as given by equation 7.

SV=[S ₁ ,S ₂ ,S ₃]^(T)=[|S| ²−|C| ²Re(S·C*)]  (7)

In equation 7, Re( ) is a real number operator that outputs the realcomponent of its argument and Im( ) is an imaginary number operator thatoutputs the imaginary component of its argument. In other words, in thisideal case, photodiode 164 in SVR 160 may output S₁ as |S|²−|C|²,photodiode 168 in SVR 160 may output S₂ as Re(S·C*), and photodiode 166in SVR 160 may output S₃ as Im(S·C*).

However, in practice, there is non-zero polarization rotation betweenwireless communications system 95 and device 10 (e.g., device 10 andwireless communications system 95 are imperfectly aligned) and suchrotation may change as wireless communications system 95 and/or device10 moves or changes orientation. As such, control circuitry 14 (FIG. 1 )may measure (e.g., identify, detect, gather, generate, estimate, etc.)Stokes vector SV using SVR 160, may identify (e.g., detect, generate,estimate, etc.) the polarization rotation between device 10 and wirelesscommunications system 95 using the measured Stokes vector SV, and mayactively compensate for the identified polarization rotation during thereception of subsequent THF signals from wireless communications system95.

Since the non-ideal signal polarization is randomly rotated in theoptical fiber and wireless channels, the received optical signalsRXOPT(H) and RXOPT(V) will each be an arbitrary/random mixture of thetransmitted modulated signal S and the transmitted unmodulated carrierC. SVR 160 may be used to acquire the polarization rotation (PR) betweendevice 10 and wireless communications system 95. Unlike coherentdetection, which performs PR in the Jones space, SVR 160 performs PRdetection in the Stokes space. The Stokes space may be depicted by aPoincaré sphere having a random rotation of the V and H polarizationplanes because of fiber and wireless polarization transmission. Controlcircuitry 14 may identify these planes and may de-rotate the planes toalign the V and H polarization planes with the S₂ and S₃ planes,respectively, in the Poincaré sphere. To recover the received signal,control circuitry 14 may identify (e.g., detect, generate, estimate,etc.) an SV rotation matrix X of the combined channel and may use the SVrotation matrix X to rotate the stokes vector SV forsubsequently-received signals to align with those at the transmitter(wireless communications system 95).

If desired, wireless communications system 95 may transmit test datathat allows device 10 to identify rotation matrix X at any giveninstant. FIG. 11 is a flow chart of illustrative operations involved incontrolling wireless communications system 95 and device 10 to identifyrotation matrix X for use in performing subsequent communications whilemitigating polarization rotations and other impairments between device10 and wireless communications system 95. Operations 172, 176, 180, and184 of FIG. 11 may be performed by device 10 of FIG. 10 (e.g., a firstdevice 10). Operations 170, 174, 178, and 182 of FIG. 11 may beperformed by wireless communications system 95 of FIG. 9 (e.g., at leasta second device 10). The test data transmitted by wirelesscommunications system 95 may include a series of test data such as aseries of training symbols. The training symbols may, for example, beadded before each transmit signal frame in the time domain.

At operation 170, wireless communications system 95 may transmitvertically polarized combined signal S′(V) and horizontally polarizedcombined signal C′(H) (FIG. 9 ), where vertically polarized combinedsignal S′(V) includes a first training (test) symbol from a series oftraining (test) symbols. The training symbol may include a predeterminedpattern or series of bits that are known to both device 10 and wirelesscommunications system 95. Wireless communications system 95 may, forexample, append the first training symbol to the beginning of a firstsignal frame in the time domain. The first training symbol may, forexample, involve the transmission of no modulated signals, therebyresulting in a Jones vector of [0, 1]. This may correspond to anexpected Stokes vector SVE at device 10 of [−1,0,0]^(T), which ispredetermined and known to device 10 (e.g., which is expected by device10 during the scheduled transmission of the first training symbol).Equation 8 characterizes the Stokes vector SV measured by SVR 160 ondevice 10 in response to the first training symbol.

SV=X·SVE   (8)

Equation 9 expands the vectors and matrices of Equation 7 to show eachelement S of the Stokes vector SV measured using SVR 160 on device 10,each element x of SV rotation matrix X, and each element of the expectedStokes vector SVE for the first training symbol.

$\begin{matrix}{\begin{pmatrix}S_{1} \\S_{2} \\S_{3}\end{pmatrix} = {\begin{pmatrix}x_{11} & x_{12} & x_{13} \\x_{21} & x_{22} & x_{23} \\x_{31} & x_{32} & x_{33}\end{pmatrix}\begin{pmatrix}{- 1} \\0 \\0\end{pmatrix}}} & (9)\end{matrix}$

At operation 172, device 10 may receive the first training symboltransmitted by wireless communications system 95 and may provide thecorresponding optical signals RXOPT(H) and RXOPT(V) to SVR 160. SVR 160may generate Stokes vector SV based on the received first trainingsymbol. As shown by equation 9, the first training symbol will cause themultiplication of SV rotation matrix X and expected Stokes vector[−1,0,0]^(T). to preserve only the first column of SV rotation matrix X(e.g., [x₁₁, x₂₁, x₃₁]^(T)) while the remaining columns are equal tozero. As such, control circuitry 14 on device 10 may identify (e.g.,measure, detect, determine, generate, etc.) the first column of SVrotation matrix X by using SVR 160 to generate Stokes vector SV inresponse to the first training symbol received in optical signalsRXOPT(H) and RXOPT(V) (e.g., where the element S₁ output by photodiode164 is equal to −x₁₁, the element S₂ output by photodiode 168 is equalto −x₂₁, and the element S₃ output by photodiode 166 is equal to −x₃₁).Subsequent training symbols may be used to identify the remainingcolumns of SV rotation matrix X.

At operation 174, wireless communications system 95 may transmitvertically polarized combined signal S′(V) and horizontally polarizedcombined signal C′(H) (FIG. 9 ), where vertically polarized combinedsignal S′(V) includes a second training (test) symbol from the series oftraining (test) symbols. The power of horizontally polarized combinedsignal C′(H) may remain constant for the first and second trainingsymbols. Wireless communications system 95 may, for example, append thesecond training symbol to the beginning of a second signal frame in thetime domain. The second training symbol may, for example, involve thetransmission of a real signal with a constant power that is the same asthat of the carrier, thereby resulting in a Jones vector of [1, 1]. Thismay correspond to an expected Stokes vector SVE at device 10 of[0,1,0]^(T), which is predetermined and known to device 10 (e.g., whichis expected by device 10 during the scheduled transmission of the secondtraining symbol). Equation 10 characterizes the Stokes vector SVmeasured by SVR 160 on device 10 in response to the second trainingsymbol.

$\begin{matrix}{\begin{pmatrix}S_{1} \\S_{2} \\S_{3}\end{pmatrix} = {\begin{pmatrix}x_{11} & x_{12} & x_{13} \\x_{21} & x_{22} & x_{23} \\x_{31} & x_{32} & x_{33}\end{pmatrix}\begin{pmatrix}0 \\1 \\0\end{pmatrix}}} & (10)\end{matrix}$

At operation 176, device 10 may receive the second training symboltransmitted by wireless communications system 95 and may provide thecorresponding optical signals RXOPT(H) and RXOPT(V) to SVR 160. SVR 160may generate Stokes vector SV based on the received second trainingsymbol. As shown by equation 10, the second training symbol will causethe multiplication of SV rotation matrix X and expected Stokes vector[0,1,0]^(T) to preserve only the second column of SV rotation matrix X(e.g., [x₁₂, x₂₂, x₃₂]^(T)) while the remaining columns are equal tozero. As such, control circuitry 14 on device 10 may identify (e.g.,measure, detect, determine, generate, etc.) the second column of SVrotation matrix X by using SVR 160 to generate Stokes vector SV inresponse to the second training symbol received in optical signalsRXOPT(H) and RXOPT(V) (e.g., where the element S₁ output by photodiode164 is equal to x₁₂, the element S₂ output by photodiode 168 is equal tox₂₂, and the element S₃ output by photodiode 166 is equal to x₃₂).

At operation 178, wireless communications system 95 may transmitvertically polarized combined signal S′(V) and horizontally polarizedcombined signal C′(H) (FIG. 9 ), where vertically polarized combinedsignal S′(V) includes a third training (test) symbol from the series oftraining (test) symbols. The power of horizontally polarized combinedsignal C′(H) may remain constant between the first, second, and thirdtraining symbols. Wireless communications system 95 may, for example,append the third training symbol to the beginning of a third signalframe in the time domain. The third training symbol may, for example, berepresented by a Jones vector of [j, 1]. This may correspond to anexpected Stokes vector SVE at device 10 of [0,0,1]^(T), which ispredetermined and known to device 10 (e.g., which is expected by device10 during the scheduled transmission of the second training symbol).Equation 11 characterizes the Stokes vector SV measured by SVR 160 ondevice 10 in response to the third training symbol.

$\begin{matrix}{\begin{pmatrix}S_{1} \\S_{2} \\S_{3}\end{pmatrix} = {\begin{pmatrix}x_{11} & x_{12} & x_{13} \\x_{21} & x_{22} & x_{23} \\x_{31} & x_{32} & x_{33}\end{pmatrix}\begin{pmatrix}0 \\0 \\1\end{pmatrix}}} & (11)\end{matrix}$

At operation 180, device 10 may receive the third training symboltransmitted by wireless communications system 95 and may provide thecorresponding optical signals RXOPT(H) and RXOPT(V) to SVR 160. SVR 160may generate Stokes vector SV based on the received third trainingsymbol. As shown by equation 11, the third training symbol will causethe multiplication of SV rotation matrix X and expected Stokes vector[0,1,0]^(T) to preserve only the third column of SV rotation matrix X(e.g., [x₁₃, x₂₃, x₃₃]^(T)) while the remaining columns are equal tozero. As such, control circuitry 14 on device 10 may identify (e.g.,measure, detect, determine, generate, etc.) the third column of SVrotation matrix X by using SVR 160 to generate Stokes vector SV inresponse to the third training symbol received in optical signalsRXOPT(H) and RXOPT(V) (e.g., where the element S₁ output by photodiode164 is equal to x₁₃, the element S₂ output by photodiode 168 is equal tox₂₃, and the element S₃ output by photodiode 166 is equal to x₃₃). Inthis way, device 10 may use the three training symbols to measure theelements in each column of SV rotation matrix X. Device 10 maythereafter have knowledge of the polarization rotation between device 10and communications system 95.

At operation 182, wireless communications system 95 may continue totransmit wireless data to device 10 using THF signals 32H and 32V (e.g.,using vertically polarized combined signal S′(V) and horizontallypolarized combined signal C′(H) of FIG. 9 ).

At operation 184, device 10 may receive the transmitted wireless data.SVR 160 on device 10 may generate Stokes vector SV using the receivedwireless data and may multiply Stokes vector SV (e.g., the receivedwireless data) by the generated SV rotation matrix X to reverse,mitigate, or compensate for the polarization rotation between device 10and wireless communications system 95 and other related optical/wirelessimpairments. Multiplication of the measured Stokes vector SV by SVrotation matrix X may, for example, recover the transmitted Stokesvector SV as [|S|²−|C|², Re(S·C*), Im(S·C*)], thereby allowing device 10to properly receive the transmitted wireless data while optimizingcommunications efficiency. In other words, by combining the second andthird elements of the measured Stokes vector SV, control circuitry 14 ondevice 10 may recover a final output that has the full phase diversityof modulated signal S, from which the input signal is fully recoveredwithout being affected by chromatic dispersion-related fading. Thenonlinearity term is grouped into the first element (component) of themeasured Stokes vector SV without affecting the recovered signalsderived from the second and third elements (components) of the measuredStokes vector SV.

Processing may subsequently loop back to operation 170 via path 186 toupdate the rotation matrix X over time (e.g., after a predetermined timeperiod has elapsed, at a scheduled time, in response to a user input orapplication call, in response to the sensed movement and/or rotation ofdevice 10, etc.). The example of FIG. 11 is merely illustrative. Ifdesired, device 10 may transmit the identified SV rotation matrix X towireless communications system 95 (e.g., at operation 180) and wirelesscommunications system 95 may pre-compensate subsequently transmittedwireless data for the polarization rotation using SV rotation matrix X(e.g., at operation 182). Other methods for detecting Stokes vector SVmay be used if desired. These operations may be generalized to generateStokes Vectors SV of any desired size and to recover the elements of anSV rotation matrix X of any desired size. If desired, otherpolarizations may be used for THF signal transmission. Other modulationformats may be used if desired.

Device 10 may gather and/or use personally identifiable information. Itis well understood that the use of personally identifiable informationshould follow privacy policies and practices that are generallyrecognized as meeting or exceeding industry or governmental requirementsfor maintaining the privacy of users. In particular, personallyidentifiable information data should be managed and handled so as tominimize risks of unintentional or unauthorized access or use, and thenature of authorized use should be clearly indicated to users. Theoptical components described herein (e.g., MZM modulator(s),waveguide(s), phase shifter(s), UTC PD(s), etc.) may be implemented inplasmonics technology if desired.

The methods and operations described above in connection with FIGS. 1-13(e.g., the operations of FIGS. 10 and 13 ) may be performed by thecomponents of device 10 using software, firmware, and/or hardware (e.g.,dedicated circuitry or hardware). Software code for performing theseoperations may be stored on non-transitory computer readable storagemedia (e.g., tangible computer readable storage media) stored on one ormore of the components of device 10 (e.g., storage circuitry 16 of FIG.1 ). The software code may sometimes be referred to as software, data,instructions, program instructions, or code. The non-transitory computerreadable storage media may include drives, non-volatile memory such asnon-volatile random-access memory (NVRAM), removable flash drives orother removable media, other types of random-access memory, etc.Software stored on the non-transitory computer readable storage mediamay be executed by processing circuitry on one or more of the componentsof device 10 (e.g., processing circuitry 18 of FIG. 1 , etc.). Theprocessing circuitry may include microprocessors, central processingunits (CPUs), application-specific integrated circuits with processingcircuitry, or other processing circuitry.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device comprising: a first antennaradiating element configured to receive a first wireless signal of afirst polarization; a second antenna radiating element configured toreceive a second wireless signal of a second polarization that isdifferent from the first polarization; a first photodiode coupled to thefirst antenna radiating element and configured to convert the firstwireless signal into a first optical signal; a second photodiode coupledto the second antenna radiating element and configured to convert thesecond wireless signal into a second optical signal; and a receivercoupled to the first photodiode over a first optical path and coupled tothe second photodiode over a second optical path.
 2. The electronicdevice of claim 1, wherein the first photodiode comprises a firstuni-travelling-carrier photodiode (UTC PD) and the second photodiodecomprises a second UTC PD.
 3. The electronic device of claim 1, whereinthe second antenna radiating element at least partially overlaps thefirst antenna radiating element.
 4. The electronic device of claim 3,wherein the first antenna radiating element comprises a first planardipole element and the second antenna radiating element comprises asecond planar dipole element oriented orthogonal to the first planardipole element.
 5. The electronic device of claim 1, wherein the firstpolarization is orthogonal to the second polarization.
 6. The electronicdevice of claim 1, wherein the receiver comprises a Stokes vectorreceiver.
 7. The electronic device of claim 6, wherein the Stokes vectorreceiver comprises: a first optical coupler coupled to the first opticalpath; a second optical coupler coupled to the second optical path; afirst photodiode coupled to the first optical coupler and the secondoptical coupler; a second photodiode; a third photodiode; and a mixingdevice coupled to the first optical coupler, the second optical coupler,the first photodiode, the second photodiode, and the third photodiode.8. The electronic device of claim 7, wherein the first photodiode isconfigured to generate a first element of a Stokes vector based on thefirst and second optical signals, the second photodiode is configured togenerate a second element of the Stokes vector based on first outputs ofthe mixing device, and the third photodiode is configured to generate athird element of the Stokes vector based on second outputs of the mixingdevice.
 9. The electronic device of claim 6, wherein the Stokes vectorreceiver is configured to generate a Stokes vector based on the firstoptical signal and the second optical signal, the electronic devicefurther comprising: one or more processors configured to mitigate apolarization rotation between the electronic device and a transmittingdevice based at least in part on the Stokes vector.
 10. The electronicdevice of claim 1, further comprising: a light source configured to emitan optical local oscillator (LO) signal, wherein the first photodiode isconfigured to convert the first wireless signal using the optical LOsignal and the second photodiode is configured to convert the secondwireless signal using the optical LO signal.
 11. The electronic deviceof claim 10, wherein the light source comprises a vertical cavitysurface emitting laser (VCSEL).
 12. A method of performing wirelesscommunications using an electronic device, the method comprising: withone or more antennas, receiving first wireless signals of a firstpolarization and second wireless signals of a second polarization thatis different from the first polarization; with a first photodiode,converting the first wireless signals into first optical signals; with asecond photodiode, converting the second wireless signals into secondoptical signals; with a receiver, generating Stokes vectors based on thefirst optical signals and the second optical signals; with one or moreprocessors, generating a rotation matrix based on the Stokes vectors;and with the one or more processors, applying the rotation matrix towireless data in subsequent wireless signals received using the one ormore antennas.
 13. The method of claim 12, wherein generating therotation matrix comprises: generating a first column of the rotationmatrix based on a first training sequence received in at least the firstwireless signals; generating a second column of the rotation matrixbased on a second training sequence received in at least the firstwireless signals after the first training sequence has been received;and generating a third column of the rotation matrix based on a thirdtraining sequence received in at least the first wireless signals afterthe second training sequence has been received.
 14. The method of claim12, wherein the subsequent wireless signals include third wirelesssignals of the first polarization and fourth wireless signals of thesecond polarization and applying the rotation matrix to the subsequentwireless signals comprises: with the one or more antennas, receiving thethird wireless signals and the fourth wireless signals; with the firstphotodiode, converting the third wireless signals into third opticalsignals; with the second photodiode, converting the fourth wirelesssignals into fourth optical signals; with the receiver, generating anadditional Stokes vector based on the third optical signals and thefourth optical signals; and with one or more processors, multiplying theadditional Stokes vector by the rotation matrix.
 15. The method of claim12, wherein receiving the first wireless signals and the second wirelesssignals comprises receiving the first wireless signals and the secondwireless signals at a frequency greater than 100 GHz.
 16. The method ofclaim 12 wherein converting the first wireless signals into the firstoptical signals comprises converting the first wireless signals into thefirst optical signals using an optical local oscillator (LO) signal andwherein converting the second wireless signals into the second opticalsignals comprises converting the second wireless signals into the secondoptical signals using the optical LO signal.
 17. A wirelesscommunication system comprising: a first photodiode; a first antennacoupled to the first photodiode; a second photodiode; a second antennacoupled to the second photodiode; a first light source configured togenerate a first optical signal at a first frequency and having a firstpolarization and configured to generate a second optical signal at thefirst frequency and having a second polarization orthogonal to the firstpolarization; a second light source configured to generate a thirdoptical signal at a second frequency that is different from the firstfrequency; and an optical combiner configured to combine the firstoptical signal, the second optical signal, and the third optical signalonto an optical path, the optical path being configured to illuminatethe first photodiode using the first optical signal and the thirdoptical signal and being configured to illuminate the second photodiodeusing the second optical signal and the third optical signal, the firstphotodiode being configured to transmit first wireless signals havingthe first polarization over the first antenna based on the first opticalsignal and the third optical signal, and the second photodiode beingconfigured to transmit second wireless signals having the secondpolarization over the second antenna based on the second optical signaland the third optical signal.
 18. The wireless communication system ofclaim 17, further comprising: an optical modulator configured tomodulate the first optical signal using a series of first training data,second training data that is different from the first training data, andthird training data that is different from the third training data. 19.The wireless communication system of claim 18, wherein the firsttraining data corresponds to a first Stokes vector at a receiver, thesecond training data corresponds to a second Stokes vector at thereceiver, and the third training data corresponds to a third Stokesvector at the receiver.
 20. The wireless communication system 19,wherein the second optical signal comprises an unmodulated carrier.